Due to continuing technological advances, a size of electronic components (e.g., semiconductor integrated circuits) has been continuing to decrease at a tremendous rate. Many of these electronic components need a clock, and in order for the components to keep shrinking in size and still include a clock, a clock size must be able to shrink at least commensurately with other devices of the component.
One clock approach is to use a crystal (e.g., quartz) resonator as a precise frequency standard. Quartz can advantageously provide parts-per-million frequency stability (and, when calibrated, accuracy). Quartz is also advantageously very insensitive to temperature variations. Unfortunately, a quartz crystal resonator is a piezoelectric resonator, and the physics of piezoelectric resonators places limits on how much the resonator can actually be reduced in size.
That is, piezoelectric resonators rely upon a surface or body elastic wave that reflects off the sides of the element, and thus an overall size of the resonator is what determines the resonant frequency. For solids, elastic waves travel at about 10 Km/sec. Thus, if one needs a ˜1 MHz resonator, one must use a device of ˜0.1 cm typical dimension. Increasing the resonance frequency to further shrink the size of the resonator is not practical due to rapidly increasing acoustic losses in the bulk material. Hence, crystal resonators are not viable candidates for the degree of clock shrinkage required for continued electronic component miniaturization.
Another clock approach is to use micro-electro mechanical systems (MEMS) oscillators. However, MENS oscillators disadvantageously offer poor aging, shock, and temperature stability.
What are needed are further clock arrangements offering further degrees of miniaturization, while also providing high accuracy, and temperature, aging and shock stability.